Self- and Cross-Pollination in Argane Tree and their Implications on Breeding Programs.

The argane tree (Argania spinosa L.) is a mostly self-incompatible species that must be cross-pollination. However, the cross-pollination is often insufficient to obtain a desirable fruit yield in the absence of compatibility between the orchard's argane trees. Proper pollination design is therefore essential to ensure a supply of compatible pollen. In this study, pollen germination and pollen development following cross- and self-pollination were investigated in A. spinosa. The choice of compatible parents or a pollinizer is currently a new research topic for the production of argane fruits in the framework of argane farming programs. Different pollination experiments were designed with two main objectives: (i) to study cross/self-(in)compatibility in the argane tree, and (ii) to determine the degree of compatibility between selected superior genotypes for pollination strategies to improve fruit set in argane orchards. Thus, to determine if a pollination deficit exists, experiments were carried out on 14 genotypes, and 5421 flowers served as sampling. The germination rate of pollen was lower than 50% for three genotypes, and only four genotypes bloom twice a year. From cross-pollination trials, traits related to the mother trees, such as the shape of the fruit and fruit ripening duration, are not influenced by the gene flow transmitted by pollens. Self-pollination was very low (0.2%) for both hand- and free self-pollination but the highest fruit set rate observed was 5.3%. Based on the pollen effect study results, it can be concluded that different pollen sources affected the fruit set. Thus, the choice of an efficient pollinizer genotype must be inter-compatible with the main variety, bloom at the same time, and be regular (no alternation). This is the first time that a pollinizer tree was reported and studied for argane. To meet future argane farming requirements, the number and location of compatible pollinizers is very important in the argane orchard design. This design of pollination remains to be checked by alternately planting a row of pollinizer trees or inter-rows with main varieties.

Comprehensive comparison of the chemical and structural characterization of landfill leachate and leonardite humic fractions.

Humic substances (HS) are complex and heterogeneous mixtures of organic compounds that occur everywhere in the environment. They represent most of the dissolved organic matter in soils, sediments (fossil), water, and landfills. The exact structure of HS macromolecules has not yet been determined because of their complexity and heterogeneity. Various descriptions of HS are used depending on specific environments of origin and research interests. In order to improve the understanding of the structure of HS extracted from landfill leachate (LHS) and commercial HS from leonardite (HHS), this study sought to compare the composition and characterization of the structure of LHS and HHS using elemental composition, chromatographic (high-performance liquid chromatography (HPLC)), and spectroscopic techniques (UV-vis, FTIR, NMR, and MALDI-TOF). The results showed that LHS molecules have a lower molecular weight and less aromatic structure than HHS molecules. The characteristics of functional groups of both LHS and HHS, however, were basically similar, but there was some differences in absorbance intensity. There were also less aliphatic and acidic functional groups and more aromatic and polyphenolic compounds in the humic acid (HA) fraction than in the fulvic acid (FA) and other molecules (OM) fractions of both origins. The differences between LHS and HHS might be due to the time course of humification. Combining the results obtained from these analytical techniques cold improve our understanding of the structure of HS of different origins and thus enhance their potential use.

Change in ATP-binding cassette B1/19, glutamine synthetase and alcohol dehydrogenase gene expression during root elongation in Betula pendula Roth and Alnus glutinosa L. Gaertn in response to leachate and leonardite humic substances.

Humic substances (HS) are complex and heterogeneous compounds of humified organic matter resulting from the chemical and microbiological decomposition of organic residues. HS have a positive effect on plant growth and development by improving soil structure and fertility. They have long been recognized as plant growth-promoting substances, particularly with regard to influencing nutrient uptake, root growth and architecture. The biochemical and molecular mechanisms through which HS influence plant physiology are not well understood. This study evaluated the bioactivity of landfill leachate and leonardite HS on alder (Alnus glutinosa L. Gaertn) and birch (Betula pendula Roth) during root elongation in vitro. Changes in root development were studied in relation to auxin, carbon and nitrogen metabolisms, as well as to the stress adaptive response. The cDNA fragments of putative genes encoding two ATP-binding cassette (ABC) transporters (ABCB1 and ABCB19) belonging to the B subfamily of plant ABC auxin transporters were cloned and sequenced. Molecular data indicate that HS and their humic acid (HA) fractions induce root growth by influencing polar auxin transport (PAT), as illustrated by the modulation of the ABCB transporter transcript levels (ABCB1 and ABCB19). There were also changes in alcohol dehydrogenase (ADH) and glutamine synthetase (GS) gene transcript levels in response to HS exposure. These findings confirmed that humic matter affects plant growth and development through various metabolic pathways, including hormonal, carbon and nitrogen metabolisms and stress response or signalization.